Transformer having a wound core around linear conductors

ABSTRACT

A transformer having a pair of insulated wires disposed generally adjacent and parallel to each other, one wire being the primary and the other wire being the secondary of the transformer, said insulated wires being wrapped by a film of insulating material. The wrapped wires have a ferrous foil, coated with an insulating film, wrapped in several layers tightly therearound. The assembly of wrapped wires with foil therearound is bound together by a binder. The inner margin of the foil is adhered to the outer margin of the film of insulating material to anchor it and the outer margin of the foil is adhered to the binder. The binder is turned inward at the axially spaced ends of the transformer to protect the foil at those ends. A method of making the transformer is disclosed, including the steps of disposing the insulated wires as stated, wrapping the insulation material therearound, wrapping the foil therearound, and binding the wrapped foil in place.

United States Patent [72] Inventors Robert L. Arntz;

John R. Marker, J r., Mansfield, Ohio [21] Appl. No. 823,326

[22] Filed May 9, 1969 [45] Patented May 4, 1971 [73] Assignee DominionElectric Corporation Mansfield, Ohio [54] TRANSFORMER HAVING A WOUNDCORE AROUND LINEAR CONDUCTORS 4 Claims, 2 Drawing Figs.

[52] U.S. Cl 336/175, 336/213, 336/219 [51] Int.Cl 1101f 17/06 [50]Field ofSearch 336/173, 174, 175,219,213; 178/45; 174/102, 107, 105, 36,1 17.1

[56] References Cited UNlTED STATES PATENTS 476,816 6/1892 Pfannkuche336/175X 1,763,150 6/1930 Hebrew 336/175 2,519,495 8/1950 Nesbitt et a1336/219X Primary ExaminerThomas J. Kozma Attorney-Woodling, Krost,Granger and Rust ABSTRACT: A transformer having a pair of insulatedwires disposed generally adjacent and parallel to each other, one wirebeing the primary and the other wire being the secondary of thetransformer, said insulated wires being wrapped by a film of insulatingmaterial. The wrapped wires have a ferrous foil, coated with aninsulating film, wrapped in several layers tightly therearound. Theassembly of wrapped wires with foil therearound is bound together by abinder. The inner margin of the foil is adhered to the outer margin ofthe film of insulating material to anchor it and the outer margin of thefoil is adhered to the binder. The binder is turned inward at theaxially spaced ends of the transformer to protect the foil at thoseends. A method of making the transformer is disclosed, including thesteps of disposing the insulated wires as stated, wrapping theinsulation material therearound, wrapping the foil therearound, andbinding the wrapped foil in place.

PATENI'EUMAY 4197: 3,577,110

INVENTORS. P05 E RT L .A KN Tl JOHN E. MAEKEE JE.

. l TRANSFORMER HAVING A WOUND CORE AROUND 1 LINEAR CONDUCTORS An objectof our invention is to provide an improved transformer particularlyadapted for isolating two circuits in an electric appliance.

-Another object is the provision for an economically built transformerproviding means for both isolating electric circuits and fortransfonning the electrical energy from one circuit to the other.

Another object is the provision of an improved method for building anelectric transformer that is both efficient and economical.

Another object is the provision of an electric transformer having arelatively long length and relatively small diameter or transversedimension so as to adapt itself to limited space in an appliance such asalong the adjoining walls of an electric toaster.

Other objects and a fuller understanding of this invention maybe had byreferring to the following description and claims, taken in conjunctionwith the accompanying drawings, in which:

FIG. 1 is a longitudinal view, partially in section, of our improvedtransformer in the preferred form thereof; and

FIG. 2 is an enlarged cross-sectional line 2-2 of FIG. 1.

Our transformer has two electric wires 11 and 12 disposed substantiallyparallel to each other. Each of these wires is of the usual multistrandtype, as depicted for example in FIG. 2. In the embodiment illustrated,wire 11 is denoted as the primary wire 'of the transformer and wire 12as the secondary wire of the transfonner. It is understood, of course,that this could be in the reverse order depending upon the transform ingcharacteristics desired in the ultimate structure.

Wire 11 has the usual insulation 13 of rubberlike material extendingfully therearound, the outermost surface of the insulation 13 having afabric outer layer molded therewith in the usual manner. Also disposedentirely around the wire 12 is an insulation 14 of rubberlike material.The outermost surface of the insulation 14 is covered by a fabriccoating 16 molded therewith.- The wires 11 and 12 and the insulations,made up ofl3 ad15 aroundwire 11 and made up of 14 and 16 around wire 12,are constructed in the usual and well-known manner. Wrapped around bothof the insulated wires is a sheet of pliable electrical insulatingplastic material 17. A suitable plastic material for this purposeisknown under the trademark Mylar". Mylar" is the registered trademark ofE. 1. DuPont de Nemours & Company for its polyester film. It isrelatively thin pliable film having good electrical insulatingcharacteristics. Preferably, the innermost marginal edge of the plasticsheet 17 is adhered by a suitable adhesive to the outer surface of oneof the insulated wires; for example, the innermost marginal edge portionof sheet 17 is shown adhered to the fabric coating 16 around theinsulation 14 of wire 12. At least there is one complete turn aroundboth of the insulated wires and the sheet 17 overlaps itself to providefor a complete covering around the two wires.

Next wound around the assembly of the insulated wires and the sheet 17wrapped therearound is a plurality of layers of a ferrous foil 18.Preferably, the foil 18 is of a suitable steel appropriate for atransformer and preferably has a thickness of on the order of about0.002 inch to about 0.004 inch. The foil should be thin and flexibleenough to be rolled tightly in concentric adjacent layers around theassembly of insulated wires.

Before being so wrapped around the assembly, the steel foil is coated onboth sides with an epoxy phenolic or other suitable electric insulatingmaterial which is thin and flexible enough to maintain its insulatingcharacteristics while being bent in conformity with the foil as it istightly wrapped around in the form shown.

' Preferably, we anchor the inner marginal edge portion of the foil l8to the outer marginal edge portion of the sheet 17.

' By having the several layers of material adhered to each other assuggested a tight wrap is obtained whereby the several view takenthrough the layers are closely adjacent to each other and ininterengagement, except for the coating thereon, as shown in theenlarged view of FIG. 2.

To provide for the required flexibility of the foil 18 to accommodateitself to the structure shown, the steel foil may be annealed orotherwise treated prior to being coated with the epoxy phenolic.

The tightly wrapped layers of foil 18 are held in such tightly wrappedposition by a binder 19. The inner marginal edge portion of binder 19 ispreferably adhered to the outer marginal edge portion of the foil 18 soas to provide an anchor for the inner edge portion of binder, 19. Binder19 is preferably a sheet of resin impregnated fabric material which isflexible and strong enough to provide the binding function of holdingthe entire assembly together in the position shown in FIGS. 1 and 2. Theouter binder 19 preferably extends along the length of the layers offoil 18 and somewhat beyond the ends thereof. The opposite extendingends of the binder 19 are then crimped radially inward as shown in FIG.1 .to substantially seal and enclose the interior of the transformeragainst moisture. Also the binder 19 provides electrical insulationaround the assembly of ferrous foil 18 about the two insulated wires.Our invention includes the method'herein described as well as theresulting transformer. A very economically fabricated transformer isthus built and which transformer is particularly adaptable for suchpurposes as isolation of two circuits or for providing electricaltransformation of energy in an economical and simple manner. Thetransformer is also particularly adaptable to fit into confined spacesrequiring a relatively long transformer with a relatively minimumtransverse dimension. For example, the diameter or transverse dimensionof the transformer illustrated in the drawings is seen as being but arelatively small fraction of the overall length of the transformer. Aparticular advantage of our transformer is found in its use as anisolating transformer in an electric bread toaster wherein it is desiredto minimize the opportunity for electric shock to the user by having aone circuit isolated from another circuit.

Although this invention has been described in its preferred form andpreferred practice with a certain degree of particularity, it isunderstood that the present disclosure of the preferred form andpreferred practice has been made only by way of example and thatnumerous changes in the details of construction and the combination andarrangement of parts and steps may be resorted to without departing fromthe spirit and the scope of the invention as hereinafter claimed.

The present disclosure includes that contained in the appended claims,as well as that of the foregoing description.

We claim:

1. An isolating transformer comprising the combination of a first lengthof wire providing the primary element of the transformer, a secondlength of wire providing the secondary element of the transformer, firstinsulating means insulating said primary element and secondary elementfrom each other, second insulating means wound around both said primaryelement and secondary element along the length thereof, a sheet offerrous foil outwardly of said second insulating means wound tightly ina plurality of overlying layers around said assembly of primary andsecondary elements and said first and second insulating means, saidwound foil requiring binding to maintain it in tightly wound position,and a flexible binder wrapped tightly around said wound sheet of ferrousfoil to constrain and bind the same wound tightly around said assembly,said first insulating means comprising insulation completely around eachof said first and second lengths of wire whereby the insulation betweenthe two wire lengths includes the insulation on both said wire lengths,and in which second insulating means comprises a sheet of thin plasticfilm wound in a plurality of overlying layers around the insulated firstand second wire lengths, said sheet of thin plastic film along its outerterminal margin being adhered to the inner terminal margin of saidferrous foil to anchor the same wound around the said assembly.

2. An isolating transformer as claimed in claim 1, and in which-saidbinder is a 'sheet of resin impregnated glass fiber fabric having itsinner terminal margin adhered to the outer terminal margin of said sheetof ferrous foil, the binder tightly holding the ferrous foil woundaround said assembly.

3. An isolating transformer as claimed in claim 2, and in which saidferrous foil is coated on both sides with an insulating film having thecharacteristics of an epoxy phenolic.

4. A transformer comprising a longitudinally extending primary wire, alongitudinally extending secondary wire disposed generally adjacent andparallel to said primary wire, each of said wires being covered byinsulation, said wires being insulated from each other by the insulationon both the wires, a sheet of plastic film having good electricalinsulating characbeing adhered to each other to anchor the inner marginof the ferrous foil, and the said binder and ferrous foil being adheredto each other to anchor the outer margin of the ferrous foil.

1. An isolating transformer comprising the combination of a first lengthof wire providing the primary element of the transformer, a secondlength of wire providing the secondary element of the transformer, firstinsulating means insulating said primary element and secondary elementfrom each other, second insulating means wound around both said primaryelement and secondary element along the length thereof, a sheet offerrous foil outwardly of said second insulating means wound tightly ina plurality of overlying layers around said assembly of primary andsecondary elements and said first and second insulating means, saidwound foil requiring binding to maintain it in tightly wound position,and a flexible binder wrapped tightly around said wound sheet of ferrousfoil to constrain and bind the same wound tightly around said assembly,said first insulating means comprising insulation completely around eachof said first and second lengths of wire whereby the insulation betweenthe two wire lengths includes the insulation on both said wire lengths,and in which second insulating means comprises a sheet of thin plasticfilm wound in a plurality of overlying layers around the insulated firstand second wire lengths, said sheet of thin plastic film along its outerterminal margin being adhered to the inner terminal margin of saidferrous foil to anchor the same wound around the said assembly.
 2. Anisolating transformer as claimed in claim 1, and in which said binder isa sheet of resin impregnated glass fiber fabric having its innerterminal margin adhered to the outer terminal margin of said sheet offerrous foil, the binder tightly holding the ferrous foil wound aroundsaid assembly.
 3. An isolating transformer as claimed in claim 2, and inwhich said ferrous foil is coated on both sides with an insulating filmhaving the characteristics of an epoxy phenolic.
 4. A transformercomprising a longitudinally extending primary wire, a longitudinallyextending secondary wire disposed generally adjacent and parallel tosaid primary wire, each of said wires being covered by insulation, saidwires being insulated from each other by the insulation on both thewires, a sheet of plastic film having good electrical insulatingcharacteristics wrapped around both said primary wire and secondary wireas a unit, a sheet of ferrous foil wrapped tightly around the assemblyof primary wire and secondary wire wrapped with said plastic film, saidwound foil requiring binding to maintain it in tightly wrapped position,and a flexible binder wrapped around the foil-wrapped assembly to holdthe same together in tightly wound position, the ends of said wiresprotruding from opposite ends of the assembly to provide leads for thetransformer, said plastic film and ferrous foil being adhered to eachother to anchor the inner margin of the ferrous foil, and the saidbinder and ferrous foil being adhered to each other to anchor the outermargin of the ferrous foil.